TITLE:   GCN CIRCULAR
NUMBER:  10039
SUBJECT: GRB 091018: GROND observations
DATE:    09/10/19 02:13:51 GMT
FROM:    Robert Filgas at MPI  <filgas@mpe.mpg.de>

R. Filgas, T. Kruehler, A. Yoldas (all MPE Garching),
S. Klose (TLS Tautenburg), and
J. Greiner (MPE Garching), report on behalf of the GROND team:

GROND (Greiner et al. 2008, PASP 120, 405), the 7-channel imager mounted
at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started
follow-up observations of GRB 091018 (Stamatikos et al. 2009, GCN 10034)
on October 18, at 23:47 UTC (~4 hrs after the burst).

For the afterglow candidate reported by Stamatikos et al. we
estimate the following preliminary magnitudes (in the AB system):

g'= 19.061 +/- 0.010
r'= 18.853 +/- 0.007
i'= 18.732 +/- 0.013
z'= 18.70  +/- 0.10
J = 18.3   +/- 0.1
H = 18.2   +/- 0.1
K = 17.9   +/- 0.1

calibrated against GROND zeropoints.